The present invention relates to a liquid crystal device that displays visible images, such as letters and numbers, by controlling the alignment of liquid crystal to modulate light. The present invention also relates to an electronic apparatus including the liquid crystal device. The present invention further relates to a manufacturing method of manufacturing such a liquid crystal device.
(1) In recent years, a liquid crystal device has found use as a visible image display part in various types of electronic apparatuses, such as a car navigation system, and a portable electronic terminal. In a well-known type of liquid crystal device, a plurality of pairs of pixel electrodes and nonlinear elements are formed on an element substrate, opposite electrodes, and a color filter as needed, are formed on an opposite substrate, the element substrate and the opposite substrate are bonded to each other, and a cell gap formed between the substrates is sealed with liquid crystal.
Consideration will now be given to a liquid crystal device using a MIM (Metal Insulator Metal) element that is a typical example of a TFD (Thin Film Diode) element as a nonlinear element. A pattern structure including the surroundings of pixel electrodes and nonlinear elements formed on an element substrate in the liquid crystal device is conventionally formed as shown in, for example, FIG. 6. Namely, a wire line 82 and a first electrode 83 are formed on a glass substrate 81, an anodized film 84 is formed thereon, and a second electrode 86 is formed on the anodized film 84. The layered structure including the first electrode 83, the anodized film 84, and the second electrode 86 forms a MIM element 87 serving as a nonlinear element. A pixel electrode 88 is formed so as to overlap with the leading end of the second electrode 86 in the MIM element 87.
The pixel electrode 88 is generally formed by photolithography. Specifically, first, an ITO (Indium Tin Oxide) film having a uniform thickness is formed on the glass substrate 81 by sputtering or the like, and then, an unnecessary part of the ITO is removed by etching, thereby forming the pixel electrode 88 in a desired pattern. In this case, a problem is that gaps G are formed between the ITO film 88xe2x80x2 and the second electrode 86 in forming the ITO film on the glass substrate 81 by sputtering or the like since the part of the ITO film 88xe2x80x2 overlapping with the second electrode 86 of the MIM element does not completely adhere to the second electrode 86.
If such gaps G are produced, when etching is performed later to pattern the ITO film 88xe2x80x2, etchant may enter the gaps G, which may cause a wire break between the second electrode 86 and the pixel electrode 88. Such a wire break can cause a dot defect in a visible image display area of the liquid crystal device. The transparent conductive film to be used as the pixel electrode may be made of SnOx, ZnOx, or the like instead of ITO. There is a fear that these film materials will insufficiently adhere to the second electrode 86. Therefore, a wire break may be caused by etching these materials.
(2) In general, the liquid crystal devices include an active-matrix liquid crystal device in that nonlinear elements are provided for respective pixels, and a passive-matrix liquid crystal device that does not use such nonlinear elements. In the active-matrix liquid crystal device, an element substrate having nonlinear elements and transparent pixel electrodes and an opposite substrate having opposite electrodes are bonded to each other, and a cell gap formed between the substrates is sealed with liquid crystal.
Element substrates and opposite substrates are not fabricated one by one, and, in general, a plurality of element substrates and opposite substrates are formed in substrate base materials having a large area, respectively. By bonding the element substrate base material and the opposite substrate base material thus fabricated, a plurality of liquid crystal panels are simultaneously formed. The element substrate base material and the opposite substrate base material are bonded such as to align alignment marks that are formed at appropriate positions thereon.
In a conventional liquid crystal device manufacturing method, in order to confirm whether the element substrate base material and the opposite substrate base material are bonded in a proper positional relationship, an image of one pixel portion in the liquid crystal panel is formed by using an image pickup device such as a CCD camera and displayed on a screen of a CRT monitor or the like, or one pixel portion is microscopically observed, whereby it is examined whether the bonded state is proper from a positional point of view.
In a conventional inspection method, for example, the peripheral line of the transparent pixel electrode on the element substrate and a predetermined reference mark on the opposite substrate side, for example, the peripheral line of an opening portion of a black matrix, are compared with each other, and it is determined whether they are in a proper positional relationship. Thereby, it is determined whether the bonded state of the element substrate and the opposite substrate is good or bad. If it is good, the device is shipped as a product. If it is bad, the device is disposed of. Since the transparent pixel electrodes formed on the element substrate side are almost colorless and transparent, however, it is very difficult to perform a precise inspection in a short time in the case of the conventional liquid crystal device that is subjected to visual inspection with reference to the transparent pixel electrodes.
(3) The present invention has been made in view of the aforementioned problems, and an object of the present invention is to improve productivity of liquid crystal devices by providing an appropriate member on the periphery of a pixel electrode.
More specifically, a first object of the present invention is to provide an appropriate member on the periphery of a pixel electrode so as to prevent contact failure due to etching between a nonlinear element and the pixel electrode, and to prevent a dot defect in a visible image display area of a liquid crystal device.
A second object of the present invention is to provide an appropriate member on the periphery of a pixel electrode so as to precisely and visually detect the amount of offset between an element substrate and an opposite substrate in a short time.
(1) In order to achieve the above first object, the present invention provides a liquid crystal device having a plurality of pixel electrodes and a nonlinear element including an element-side electrode electrically connected to the pixel electrodes, wherein the element-side electrode is shaped in a pattern formed along the edge of the pixel electrode.
According to this liquid crystal device, since a part of the element-side electrode that overlaps with the pixel electrode is shaped like a pattern formed along the edge of the pixel electrode, when divided pixel electrodes are formed by etching an ITO film, etchant is prevented from entering between the element-side electrode and the ITO film. Therefore, it is possible to prevent a wire break between the element-side electrode and the ITO film.
(2) In the configuration mentioned above, it is preferable that the element-side electrode be shaped like a ring-shaped frame along the entire peripheral edge of the pixel electrode. This makes it possible to restrict the entry of etchant as much as possible, and to thereby more reliably prevent a wire break.
(3) Preferably, the outer dimensions of the element-side electrode are larger than that of the pixel electrode. This makes it possible to more reliably prevent the entry of the etchant.
(4) Next, in order to achieve the above first object, the present invention provides an electronic apparatus including a liquid crystal device having the aforementioned configuration, and a control unit for controlling the operation of the liquid crystal device. As such an electronic apparatus, for example, a car navigation system, a portable terminal apparatus, and other various electronic apparatuses are available.
(5) In order to achieve the above second object, the present invention provides a liquid crystal device having an element substrate having a nonlinear element and a transparent pixel electrode on a substrate, and an opposite substrate opposed to the device substrate, wherein the liquid crystal element comprises a mark that overlaps with at least a part of the peripheral edge of the transparent pixel electrode in a plane manner and has a higher light-shielding ability than that of the transparent pixel electrode.
According to this liquid crystal device, since the mark overlaps with at least a part of the peripheral edge of the transparent pixel electrode in a plane manner, it can be determined, by visually comparing the mark on the element substrate and a reference mark on the opposite substrate, whether or not the positional relationship between the element substrate and the opposite substrate is proper. In particular, since the mark is formed so that it has a higher light-shielding ability than that of the transparent pixel electrode, it is easy to visually recognize. Therefore, it is possible to make a precise judgement in a short time.
(6) In the liquid crystal device having the aforementioned configuration, it is preferable that the mark be formed at least at two positions at the opposite corners of the transparent pixel electrode, and that the mark have two branch portions extending in almost perpendicular directions along two sides adjoining to the corners. When the mark is formed at two positions at the opposite corners of the transparent pixel electrode, if a predetermined region on the opposite substrate opposing a transparent pixel electrode, for example, an opening portion of a black matrix is offset from the transparent pixel electrode in a vertical direction or a horizontal direction, the offset can be detected.
When the mark includes two branch portions along two sides of the transparent pixel electrode that adjoin one corner, it is possible to easily and precisely recognize the offset of the opening portion or the like from the transparent pixel electrode both in a vertical direction and a horizontal direction.
(7) The mark may be shaped like a frame formed along the entire peripheral edge of the transparent pixel electrode. This makes it possible to detect the offset with reference to the entire periphery of the transparent pixel electrode, and to thereby achieve an even easier and more precise inspection.
(8) Some liquid crystal devices have a structure in which a nonlinear element is formed on an underlayer after the underlayer is formed on a substrate. This underlayer is made of, for example, tantalum oxide (TaOX), and has the functions of improving the adhesion of the nonlinear element, and the like. If the underlayer is present under the transparent pixel electrode, however, the transparency of the pixel area is impaired. Therefore, the underlayer in the area corresponding to the transparent pixel electrode is removed in most cases. In such a case, the peripheral edge of the removed part of the underlayer may be used as a position check mark.
(9) In the liquid crystal device of the present invention, the nonlinear element may be a two-terminal type nonlinear element. This two-terminal type nonlinear element generally includes a first electrode, an insulating film laid on the first electrode, and a second electrode laid on the insulating film. When this two-terminal type nonlinear element is used, the mark may be made of the same material as that of the first electrode or the second electrode of the two-terminal type nonlinear element. In this case, since the mark can be formed by patterning simultaneously with the patterning of the first electrode or the second electrode, the working process is not complicated.
(10) In the liquid crystal device of the present invention, the nonlinear element may be a thin-film transistor element. When this thin-film transistor element is used, the mark may be made of the material of one of the films for constituting the element, the film at least having a higher light-shielding ability than that of the pixel electrode. In this case, since the mark can be formed by patterning simultaneously with the patterning of the film, the working process is not complicated.
(11) In the liquid crystal device of the present invention, the offset is detected while comparing the mark on the element substrate side and a reference mark on the opposite substrate side. In this case, various types of marks may be available as the reference mark on the opposite substrate side. For example, when a black matrix for forming divided opening portions corresponding to pixels is formed on the opposite substrate, the peripheral edges of the black matrix opening portions may be compared with the mark. When the opposite substrate has a color filter, the peripheral edges of respective color dots, which constitute the color filter, may be compared with the mark.
(12) Next, the present invention provides a liquid crystal device manufacturing method having the step of bonding an element substrate having a nonlinear element and a transparent pixel electrode thereon and an opposite substrate opposed to the element substrate to each other, the liquid crystal device manufacturing method comprises the steps of (a) forming on the element substrate a mark having a higher light-shielding ability than that of the transparent pixel electrode so as to overlap with at least a part of the peripheral edge of the transparent pixel electrode in a plane manner, and (b) confirming with reference to the mark whether the element substrate and the opposite substrate are bonded in a proper positional relationship.
According to this manufacturing method, since the mark overlaps with at least a part of the peripheral edge of the transparent pixel electrode in a plane manner, it can be determined, by visually comparing the mark on the element substrate side and a reference mark on the opposite substrate side, whether the positional relationship between the element substrate and the opposite substrate is proper. In particular, since the mark is formed as a mark having a higher light-shielding ability than that of the transparent pixel electrode, it is easy to visually recognize. Therefore, it is possible to make a precise judgement in a short time. In this manufacturing method, the peripheral edges of opening portions of a black matrix, the peripheral edges of respective color dots in a color filter, and the like are also available as the reference mark on the opposite substrate side to be compared with the mark on the element substrate side.
(13) In the aforementioned liquid crystal device manufacturing method, the positional relationship between the element substrate and the opposite substrate may be checked by forming a black matrix for forming divided opening portions corresponding to pixels on the opposite substrate, and making positional comparison between the mark and the peripheral edges of the opening portions of the black matrix.
(14) In the aforementioned liquid crystal device manufacturing method, the positional relationship between the element substrate and the opposite substrate may be checked by forming a color film including color dots of a plurality of colors on the opposite substrate, and making positional comparison between the mark and the peripheral edges of the color dots in the color filter.